RG6 suitability

[Pyro]

I've always heard RG6 Quad is unsuitable for analogue CCTV. Can somebody please explain why?, is there an electrical characteristic that is undesirable?.
We don't use it but I have seen it used without issue on CCTV.
Thanks.

[mtv]

Most RG6 cables use a copper-clad steel centre conductor. eg a very thin coating of copper on a steel wire.

The higher RF frequencies used for TV, Satellite and FM/Digital broadcasting travel mostly on the surface of the inner conductor in coaxial cables.

This is known as the 'skin effect' and as copper is one of the better conductors, those frequencies mostly only travel along the copper outer part of the coax inner conductor.

This keeps the cost of most RG6 Quadshield much lower than if you used a coaxial cable with an all-copper centre conductor.

In instances where baseband frequencies are used, such as video and audio, the signals use all of the centre conductor, not just the surface, so they are better suited to camera cables.

Having said that, RG6 Quadshield cables will in fact work with baseband video signals, but the signal levels will be degraded by comparison to solid copper types.

This will have a greater impact with digital signals compared to analogue, particularly with long runs.

However... if it works... no need to worry about theory.

[dmaher]

^ What he said.

The shield is also an issue, ideally you want copper again for less resistance and apparently a good coverage braid is better at baseband frequencies than the foil and braid on most quad shield, which is intended for higher frequencies.

Also there is also the issue of termination. I've had issues of BNC centre pins not fitting and poor termination of the shield.

Having said that I have seen it work okay the majority of the time. But also had one occasion where a CCTV spec RG6 was water or rat damaged and replaced with RG6 quad and there was noticeable interference introduced which I confirmed with a waveform monitor.

Pelco have a document on it, I'll see if I can find it.

[Pyro]

Thanks for your responses. I've seen that to Dmaher, a trusty F-Type connector and a F to BNC adaptor seems like a more reliable solution. I've had some Issues with BNC Crimps fitting RG6.

[mtv]

I've had some Issues with BNC Crimps fitting RG6.

Are you aware there are different size BNC crimp connectors?.... eg: RG6 Dualshield, Trishield, Quadshield.

I've never had an issue when matching the right connector to the cable used.

[dmaher]

Are you aware there are different size BNC crimp connectors?.... eg: RG6 Dualshield, Trishield, Quadshield.

I've never had an issue when matching the right connector to the cable used.

I have seen some of the BNC crimps come with different size centre pins.

Typically though the supplier only has the one type of RG6 and RG59 and anything else like RG179 is a special order.

Seems like a lot of effort to get the right connector for the wrong cable.

I think it was a variety of dual/tri shield of RG59 where my BNC connectors wouldn't go over the sheath.

Never should've been used and don't have the connector to suit so just recabled it as it was a short run.

[secure]

Coax cable overview

[dmaher]

Much the same as this old Pelco document I mentioned (well Schneider does own Pelco ):

[intelliGEORGE]

I've always heard RG6 Quad is unsuitable for analogue CCTV. Can somebody please explain why?, is there an electrical characteristic that is undesirable?.
We don't use it but I have seen it used without issue on CCTV.
Thanks.

**please note: in both those posts, the RG6 I was referring to is the RG6 used for MATV/Cable installations.